1. Field of the Invention
The present invention relates an ink application process and an ink composition for use therein. More particularly, the present invention relates to a process for applying a metallic appearance to plastic substrates and the metallic printing ink composition used in the process.
2. Background
The appearance of a consumer product, specifically the product's packaging, may be very influential in a consumer's decision to purchase the product. A product packaging that stands out and catches a consumer's eye on a merchant's shelf may be more likely to be purchased by the consumer than the surrounding products. The practical treatment and design options available for certain industries and types of products, however, are often dictated by the packaging material used in connection with a particular product. For example, many products have properties which enable them to be packaged in cardboard or paperboard containers. Printing on cardboard or paperboard substrates provides the packaging designer with a relatively wide range of options for achieving a desired "look" for the packaging. In contrast, because of complications with surface texture, adherence and curing, printing on plastic containers to achieve a desired "look" is much more difficult. Accordingly, printing techniques which work well on cardboard or paperboard substrates often do not work well on plastic substrates.
Product packaging with a metallic appearance or metallic printing provides a particularly pleasing "look" to a consumer of certain products and stands out in bold relief relative to other products on a merchant's shelf. The high speed (60 units per minute or greater) in-line printing of cardboard or paperboard containers or other substrates with a metallic appearance is well known and common in the art. However, the high speed metallic printing of plastic containers, such as those commonly used in the hair care industry, presents a particular challenge primarily because of adherence and curing problems.
One method for providing a metallic appearance to a plastic product packaging substrate is referred to as hot foil stamping. Generally, hot foil stamping involves shrouding the substrate with a die containing a metallic foil material, and heating the die for a period of time such that the metallic foil material is released from the die and is transferred to and adheres to the substrate. In a typical hot foil stamping operation, approximately 7 to 10 substrate items or units may be processed in-line per minute.
Accordingly, hot foil stamping has limitations as a process for providing a metallic appearance to a plastic substrate. First, hot foil stamping process is slow and cannot be performed at typical in-line commercial ink printing speeds. Second, the foil materials utilized in the hot foil stamping process are expensive; thus, the cost per unit for applying a metallic appearance to a plastic container is significantly higher than corresponding in-line printing on cardboard substrates. Third, for many commercial ink printers, operating a hot foil stamping system for plastic substrates is inefficient. A hot foil stamping system generally cannot be adapted to the conventional commercial ink printing operations described below, and instead must operate as a separate system requiring additional space, parts, manpower, and various other costs. Accordingly, these limitations force some product packaging designers and manufacturers to sacrifice a product's appearance for economic concerns.
Thus, there exists a need for a process for providing a metallic appearance to product packaging, in particular to plastic substrates, that may be performed relatively inexpensively, efficiently and at speeds approaching typical in-line commercial ink printing speeds. Ideally, the process should provide a metallic appearance to the substrate similar to that obtained by hot foil stamping.